Protecting Australia's citrus genetic material (CT17008)
What’s it all about?
Access to healthy planting material is essential for the Australian citrus industry, with supply of disease-free, true-to-type propagation material of key importance. While diseases such as Huanglongbing and citrus variegated chlorosis (CVC) remain exotic to Australia, there are a number of graft-transmissible viruses and viroids in Australia that can cause stunting, yield loss and even death in some scion and rootstock combinations.
With this in mind, this investment will continue funding for the long-term National Citrus Repository (NCR) program for publicly owned citrus varieties. It will support the maintenance and disease testing of foundation trees in the NCR, as well as the disease testing of new Australian citrus selections entering the repository system.
The NCR is an important part of an integrated biosecurity system designed to protect the health and economic viability of the Australian citrus industry. From foundation tree budwood, Auscitrus creates daughter trees and multiplies large numbers of buds for industry. New varieties can enter the program if no known diseases are detected after pathogen testing and elimination.
Since July 2019, one new publicly owned imported variety (Shiranui) was released from post-entry quarantine and entered the repository system.
A list of all publicly owned citrus varieties held in the repository is published in the Auscitrus annual report 2018 as well as the Auscitrus Annual report 2019. Both are available through the Auscitrus website.
Repository trees are tested annually for Citrus tristeza virus (CTV). Trees in the Dareton repository screenhouse were tested for CTV in spring 2019, and trees in the EMAI repository screenhouses were tested for CTV in autumn 2020. No CTV was detected in high health status repository trees.
Inoculated repository trees tested positive for CTV in autumn 2020, except for one tree. Trees where CTV was not detected, or only weakly detected, will be re-inoculated in spring 2020.
Dareton repository trees were tested for graft-transmissible diseases in October 2019 and testing is in progress for viroids as well as a range of other citrus viruses.
Trees in the EMAI repository will be sampled and tested for graft-transmissible diseases, and any newly discovered diseases, during 2021-2222.
Since December 2018, one new publicly-owned Australian selection (K15 pomelo) entered the National Citrus Repository (NCR) system. The NCR currently holds 123 publicly-owned citrus varieties in NSW at Dareton and the Elizabeth Macarthur Agricultural Institute (EMAI).
A list of all citrus varieties held by NCR was published in the Auscitrus annual report 2018. It will also be listed in the 2019 report, after the Auscitrus AGM which is scheduled for 7 August 2019.
In autumn 2019, NCR trees in the EMAI screen house for high health status clones were tested for citrus tatterleaf virus (CTV), with no disease detected. Trees in the Dareton screen house repository will be tested in spring 2019.
Repository trees that had not previously been checked for other diseases that can be transmitted via the graft (huanglongbing, viroids, CTV) were tested.
Pathogen-tested and true-to-type citrus budwood were made available for propagation and provision to growers, ensuring availability to industry in the event of a disease outbreak.
The project team also engaged across the sector, including activities such as presenting at the Citrus Technical Forum in March 2019.
View the list of publicly owned citrus varieties held by NCR in the Auscitrus annual report 2018.
This project is a strategic levy investment in the Hort Innovation Citrus Fund